.TH llsom_sync 8 "2018 Jan 10" Lustre "Lustre Filesystem utility"
.SH NAME
llsom_sync \- Utility to sync file LSOM xattr.
.SH SYNOPSIS
.br
.B llsom_sync --mdt|-m <mdt>  --user|-u <user id>
.br
.B\t\t\t [--daemonize|-d] [--verbose|-v] [--interval|-i]
.br
.B\t\t\t [--min-age|-a] [--max-cache|-c] [--sync|-s] <lustre_mount_point>
.br

.SH DESCRIPTION
.B llsom_sync
is designed to sync file LSOM xattr in the Lustre Filesystem by
using Lustre MDT changelogs.  A changelog user must be registered
(see lctl (8) changelog_register) before using this tool.

.SH OPTIONS

.B --mdt=<mdt>
.br
The metadata device which need to be synced the LSOM xattr of files.
A changelog user must be registered for this device.

.B --user=<user id>
.br
The changelog user id for the above MDT device. See lctl(8) changelog_register.

.B --daemonize
.br
Daemonize the program. In daemon mode, the utility will scan, process the
changelog records and sync the LSOM xattr for files periodically.

.B --verbose
.br
Produce a verbose output.

.B --interval
.br
The time interval to scan the Lustre changelog and process the log record in
daemon mode.

.B --min-age
.br
The time that llsom_sync tool will not try to sync the SOM data for any files
closed less than this many seconds old. The default min-age value is 600s
(10 minutes).

.B --max-cache
.br
The total memory used for the FID cache which can be with a suffix [KkGgMm].
The default max-cache value is 256MB. For the parameter value < 100, it is
taken as the percentage of total memory size used for the FID cache instead
of the cache size.

.B --sync
.br
Sync file data to make the dirty data out of cache to ensure the blocks count
is correct when update the file LSOM xattr. This option could hurt server
performance significantly if thousands of fsync requests are sent.

.SH EXAMPLES

.TP
Register a changelog consumer for MDT lustre-MDT0000
$ cl_user=$(ssh root@mds01 lctl --device lustre-MDT0000 changelog_register -n)
.br
$ echo $cl_user
.br
cl1

.TP
After perform some file operations on the Lustre Filesystem with
mount point '/mnt/lustre' and the filesystem undergoes some changes,
sync file LSOM xattr:
$ llsom_sync --mdt=lustre-MDT0000 --user=$cl_user \\
.br
             --verbose /mnt/lustre

.TP
To deregister the changelog user (e.g. after this example, or if SOM
updates are no longer needed):
.br
$ ssh root@mds01 lctl --device lustre-MDT0000 changelog_deregister $cl_user

.SH AUTHOR
The llsom_sync command is part of the Lustre filesystem.

.SH SEE ALSO
.BR lustre (7),
.BR lctl (8)
